Photosensitive elements for converting incident radiant energy into an electrical signal are commonly used in imaging applications, for example, x-ray imagers and/or facsimile machine type devices. Hydrogenated amorphous silicon (a-Si) and alloys of a-Si are commonly used in the fabrication of photosensitive elements due to the photoelectric characteristics of a-Si and/or the relative ease of fabrication. In particular, photosensitive elements, such as photodiodes, can be formed in conjunction with associated control or switching elements, such as thin film transistors (TFTs), in relatively large area arrays, for example to form a detector panel for an x-ray imaging system or the like.
Photodiodes typically may include an island or body of photosensitive material, such as a-Si, disposed between two electrodes electrically coupled to opposite surfaces of the photodiode body. Such photodiodes typically comprise p-type material, intrinsic type material, and n-type material, referred to as PIN diodes or the like. As incident radiation is absorbed in the a-Si, holes and electrons may be produced and move toward the upper or lower surface of the photodiode dependent on the electric filed established by the electrodes. The amount of charge collected at the electrodes is a function of the energy flux of the incident light. Periodic measuring of charge collected on a photodiode, and resetting the diode to a known charge condition, may be utilized to process electrical signals generated by the photodiode in response to incident radiation, for example photons emitted from an x-ray source that impinge upon the detector panel in an x-ray imaging system.
It may be the case that a TFT array for an imaging system may be produced in a different process, at a different time, and/or at a different location, for example at a different manufacturing facility, than the process by which the diode array is produced and integrated with the TFT array to produce an operational detector panel for an x-ray imaging system of the like. Such a TFT array may be manufactured using the same and/or similar process as a TFT array for displays. However such a fabrication process, when a photodiode array is integrated with the TFT array, may result in issues deleterious to the mechanical reliability and/or integrity of the detector panel. Such issues may include, for example, that the diode film may not adhere robustly to the TFT array, that the hydrofluoric (HF) wet etchant utilized to etch off oxide and nitride to form a via structure to make contact to the source-drain (S/D) metal of the TFT may attack the S/D metal, which may be referred to as the second metal layer, or M2 metal, and/or potential long term reliability for the diode to M2 metal contacts because such M2 metal of the TFT array may include and/or otherwise comprise an aluminum alloy, typically Mo/Al/Mo and/or Mo/Al(Nd)/Mo. In general, standard processes for producing a TFT array may not be completely compatible with processes for producing a photodiode array to be integrated with the TFT array to form a detector panel for an imaging system or the like.
It will be appreciated that for simplicity and/or clarity of illustration, elements illustrated in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, if considered appropriate, reference numerals have been repeated among the figures to indicate corresponding or analogous elements.